1. Field of the Invention
This invention relates generally to semiconductor processing and, more particularly, to the fabrication of semiconductor devices, such as transistors.
2. Description of the Related Art
Transistors with high breakdown voltages are used in various applications, including for power management or amplification and for various driver systems. One approach for forming transistors with high breakdown voltage is to form the transistors in a thick and low-doped epitaxial layer. The low-doped epitaxial layer has a high resistivity, however, which can make integration with low voltage circuitry difficult.
The dielectric reduced surface field (DIELER) effect allows another approach for forming transistors with a high breakdown voltage. Devices formed to take advantage of the DIELER effect can have a shallow, elongated N-type region formed in an epitaxial layer, with a source and drain at opposite ends of the N-type region. Such devices possess a high breakdown voltage and have relatively low resistivity. However, different, e.g., even higher, breakdown voltage characteristics are desirable in some high voltage applications.
Accordingly, there is a continuing need for methods of forming semiconductor devices, such as transistors, with high breakdown voltage.